When battery power is critically low, only the alert icon and the battery icon are displayed, and the thermostat cannot control the HVAC system. Batteries must be replaced immediately. To replace the batteries in a Honeywell T6 Pro Z-Wave Programmable Thermostat. Locate the batteries by removing the battery compartment tray or cover or by removing the unit's faceplate. Carefully extract the batteries, and replace them. Be sure to place the batteries in the correct orientation. The battery-powered control unit of Honeywell thermostat systems is integral for the operation of the entire system.
5. Model-Specific Battery Replacement Guides. Here's how to replace batteries for popular Honeywell models: Honeywell T6 Pro Series: Remove the front cover. Replace with two AA batteries. Reattach the cover. Honeywell RTH9585WF: Slide out the battery tray from the bottom. Replace with fresh batteries. Slide the tray back in. Quick Table:. View step-by-step instructions of how to replace the batteries on your Honeywell T6 thermostat. SmartRent support can also walk you through how to change the.